1. Field of the Invention
The invention relates to a method for bit detection at the receiver end of differentially coded binary or quaternary PSK (PSK =phase shift keying) signals in differential-coherent demodulation. In this connection, differential-coherent demodulation is understood to mean that, instead of using a derived reference carrier for phase demodulation, the phase of the previously received signal is used as phase reference. This has the advantage that no PLL (phase-locked loop) is required for the carrier, so that the often difficult acquisition and phase control of the carrier are unnecessary.
2. Prior Art
In methods used up to now for bit detection in DPSK modulation a transmitter generates, for example at the time t=nT, where n is an integer and T is the symbol period, the complex valued signal EQU a.sub.n =exp(j.phi..sub.i), (1)
where EQU .phi..sub.i =i2.pi./M, i=0,1, . . . , M-1 (2)
mean the M equidistant phase values of the M-PSK signal in the complex signal plane (see FIG. 1).